The order includes 30 current engine option (ceo) A321s and 10 A330-300s. Airbus called the order a "strong return to Airbus" since Delta's last order with the manufacturer was placed nearly 20 years ago. The carrier currently has 158 Airbus aircraft in its commercial fleet.

"These Airbus aircraft will generate free cash flow and improve our return on invested capital from the time they enter service," said Paul Jacobson, chief financial officer at Delta.

Delta will be the first carrier operating the 242-metric ton A330-300 variant, which has an additional 500 nautical miles of extra range and the ability to carry five metric tons more payload than the standard A330-300.